Endoscope

ABSTRACT

An endoscope includes: an image sensor including: pixels for receiving light to generate image signals, and reading circuits sharing predetermined number of pixels with one another; a format converter configured to convert the image signals output from the image sensor into a predetermined format corresponding to a processing device for performing image processing on the image signals; and a connector including the format converter and configured to be connected to the processing device. The image sensor includes a color filter of a Bayer array in which a red filter for passing a red component and a first green filter for passing a green component are alternately arranged in even lines of horizontal lines of the pixels, and a second green filter for passing a green component and a blue filter for passing a blue component are alternately arranged in odd lines of the horizontal lines.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of PCT international application Ser.No. PCT/JP2016/057604 filed on Mar. 10, 2016 which designates the UnitedStates, incorporated herein by reference, and which claims the benefitof priority from Japanese Patent Application No. 2015-069762, filed onMar. 30, 2015, incorporated herein by reference.

BACKGROUND

1. Technical Field

The disclosure relates to an endoscope configured to be introduced intoa living body to capture in-vivo images.

2. Related Art

In recent years, there has been known a technology of generating animage signal of enhancing a contour of a subject in an imaging devicesuch as an endoscope (see JP 2000-115790 A). According to thistechnology, the image signal of enhancing the contour of the subject isgenerated using a first synthesized signal obtained by alternatelyreading image signals from each of odd and even lines in a horizontalline of an image sensor provided with a color filter having a Bayerarray at an exposure time and synthesizing the read image signals and asecond synthesized signal obtained alternately reading image signalsfrom each of the odd and even lines at a non-exposure time andsynthesizing the read image signals.

SUMMARY

In some embodiments, an endoscope includes: an image sensor including: aplurality of pixels arranged two-dimensionally, the plurality of pixelsbeing configured to receive external light to generate a plurality ofimage signals in accordance with a light receiving amount; and aplurality of reading circuits sharing predetermined number of pixelswith one another and configured to read the plurality of image signalsto transfer lines; a format converter configured to convert theplurality of image signals output from the image sensor into apredetermined format corresponding to a processing device for performingimage processing on the plurality of image signals; and a connectorincluding the format converter and configured to be connected to theprocessing device. The image sensor includes a color filter of a Bayerarray in which a red filter for passing a red component and a firstgreen filter for passing a green component are alternately arranged ineven lines of horizontal lines of the plurality of pixels, and a secondgreen filter for passing a green component and a blue filter for passinga blue component are alternately arranged in odd lines of the horizontallines of the plurality of pixels. The plurality of reading circuits isconfigured to: read first image signals of the plurality of imagesignals from pixels corresponding to the red filter and read secondimage signals of the plurality of image signals from pixelscorresponding to the first green filter in the even lines of thehorizontal lines of the image sensor; and read third image signals ofthe plurality of image signals from pixels corresponding to the secondgreen filter and read fourth image signals of the plurality of imagesignals from pixels corresponding to the blue filter in the odd lines ofthe horizontal lines of the image sensor. The format converter isconfigured to convert the plurality of image signals into an imageformat for the Bayer array by converting an arrangement in the colorfilter such that the first image signals and the second image signalsare alternately arranged in the even lines of the image sensor read bythe plurality of reading circuits, and the third image signals and thefourth image signals are alternately arranged in the odd lines of theimage sensor read by the plurality of reading circuits.

The above and other features, advantages and technical and industrialsignificance of this invention will be better understood by reading thefollowing detailed description of presently preferred embodiments of theinvention, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an overall configurationof an endoscope system according to a first embodiment of the presentinvention;

FIG. 2 is a block diagram illustrating functions of main parts of theendoscope system according to the first embodiment of the presentinvention;

FIG. 3 is a schematic diagram illustrating a configuration of a colorfilter;

FIG. 4 is a circuit diagram illustrating a configuration of a firstchip;

FIG. 5 is a schematic diagram illustrating an outline of a formatconverting process which is performed on even lines of a light receivingunit by a format converter;

FIG. 6 is a schematic diagram illustrating an outline of a formatconverting process which is performed on odd lines of the lightreceiving unit by the format converter;

FIG. 7 is a schematic diagram illustrating a converting method of afilter converter; and

FIGS. 8A and 8B are block diagrams illustrating functions of main partsof an endoscope system according to a second embodiment of the presentinvention.

DETAILED DESCRIPTION

Reference will be made below to exemplary embodiments of an endoscopesystem including an imaging device. The present invention is not limitedto the embodiments. The same reference numerals are used to designatethe same elements throughout the drawings. The drawings are schematicand the relation between the thickness and the width of each member andthe ratio of each member, and the like are different from the reality.Also, parts having different dimensions and ratios are included in thedrawings.

First Embodiment

Configuration of Endoscope System

FIG. 1 is a diagram schematically illustrating an overall configurationof an endoscope system according to a first embodiment of the presentinvention. An endoscope system 1 illustrated in FIG. 1 includes anendoscope 2, a transmission cable 3, a connector 5, a processor 6 (aprocessing device), a display device 7, and a light source 8.

The endoscope 2 includes an insertion portion 100 which is a part of thetransmission cable 3 and which is configured to be inserted into a bodycavity of a subject to capture an in-vivo image of the subject andoutput an image signal (image data) to the processor 6. The endoscope 2includes an imaging unit 20 (an imaging device) configured to capture anin-vivo image on one end of the transmission cable 3, that is, a distalend 101 of the insertion portion 100 inserted into the body cavity ofthe subject. An operating unit 4 for receiving various operations of theendoscope 2 is connected to a proximal end 102 of the insertion portion100. The imaging unit 20 is connected to the connector 5 by thetransmission cable 3 through the operating unit 4. An image signal of animage captured by the imaging unit 20 is output to the connector 5through the transmission cable 3, for example, having a length ofseveral meters.

The connector 5 is configured to be connected to the processor 6 and thelight source 8, performs predetermined signal processing on the imagesignals, performs analog-to-digital conversion (A/D conversion) on theimage signals, and outputs the image signals to the processor 6.

The processor 6 includes a CPU (Central Processing Unit) or the like toperform predetermined image processing on the image signals output fromthe connector 5 and to perform overall control of the endoscope system1. In the first embodiment, the processor 6 functions as a processingdevice.

The display device 7 displays an image corresponding to the imagesignals subjected to the image processing by the processor 6. Thedisplay device 7 displays various information relating to the endoscopesystem 1.

The light source 8 is configured as, for example, a halogen lamp or awhite light emitting diode (LED) and irradiates the subject withillumination light from the distal end 101 of the insertion portion 100of the endoscope 2 via the connector 5 and the transmission cable 3.

FIG. 2 is a block diagram illustrating functions of main parts of theendoscope system 1. Referring to FIG. 2, a configuration of each elementof the endoscope system 1 and an electric signal path inside theendoscope system 1 will be described in detail.

As illustrated in FIG. 2, the imaging unit 20 includes a first chip 21(an image sensor) and a second chip 22.

The first chip 21 includes a light receiving unit 23, reading units 24(reading circuits), a timing generator 25, and a color filter 26. Thelight receiving unit 23 includes a plurality of unit pixels 230 and aplurality of dummy pixels 247. The plurality of unit pixels 230 isarranged two-dimensionally in a matrix form, receives external light,and generates image signals in accordance with a light receiving amount,and outputs the image signals. The plurality of dummy pixels 247 isarranged for each transfer line (each vertical transfer line) of theplurality of unit pixels 230, and generates and outputs dummy signalsused for correcting the image signals. The reading units 24 (readingcircuits) share the light receiving unit 23 with one another for eachpredetermined unit pixel 230 and share predetermined number of pixelswith one another, and read the dummy signals and the image signalsobtained by photoelectric conversion in the light receiving unit 23. Thetiming generator 25 generates a timing signal based on a reference clocksignal and a synchronization signal input from the connector 5 andoutputs the timing signal to the reading unit 24. The color filter 26 isprovided on a light receiving surface of each of the plurality of unitpixels 230. A detail configuration of the first chip 21 will bedescribed with reference to FIG. 4.

As illustrated in FIG. 3, the color filter 26 is realized by a Bayerfilter T1 (RG_(r)BG_(b)) having a Bayer array including a red filter(hereinafter, referred to as a “R-filter”) for passing a red lightcomponent, a first green filter (hereinafter, referred to as a“G_(r)-filter”) for passing a green light component, a second greenfilter (hereinafter, referred to as a “G_(b)-filter”) for passing agreen light component, and a blue filter (hereinafter, referred to as a“B-filter”) for passing a blue light component. The R-filter, theG_(r)-filter, the B-filter, and the G_(b)-filter are arranged at eachunit pixel 230. Specifically, the color filter 26 has a configuration inwhich the R-filter and the G_(r)-filter are alternately disposed in thisorder on the even lines of the light receiving unit 23 and theG_(b)-filter and the B-filter are alternately disposed in this order onthe odd lines of the light receiving unit 23.

The second chip 22 includes a buffer 27 which serves as a transmitterfor transmitting an image signal output from the first chip 21 to theprocessor 6 via the transmission cable 3 and the connector 5. Acombination of circuits mounted on the first chip 21 and the second chip22 can be appropriately changed according to the convenience of setting.

The imaging unit 20 receives a power supply voltage VDD generated by apower supply unit 61 inside the processor 6 via the transmission cable 3together with a ground GND. A power stabilizing capacitor C1 is providedbetween the power supply voltage VDD and the ground GND supplied to theimaging unit 20.

The connector 5 is provided with an analog front-end unit 51(hereinafter, referred to as an “AFE unit 51”), an A/D converter 52, animage signal processing unit 53, and a drive signal generator 57. Theconnector 5 is connected to the processor 6, electrically connects theendoscope 2 (the imaging unit 20) and the processor 6 to each other, andserves as a relay processing unit relaying an electric signal. Theconnector 5 and the imaging unit 20 are connected to each other by thetransmission cable 3 and the connector 5 and the processor 6 areconnected to each other by, for example, a coil cable. The connector 5is also connected to the light source 8.

The AFE unit 51 receives the image signal transferred from the imagingunit 20, performs an impedance matching process on the image signal by apassive element such as a resistor, extracts an AC component by acapacitor, and determines an operation point by a voltage dividingresistor. Subsequently, the AFE unit 51 corrects the image signal (theanalog signal) and outputs the image signal to the A/D converter 52.

The A/D converter 52 converts the analog image signal input from the AFEunit 51 into a digital image signal and outputs the digital image signalto the image signal processing unit 53.

The image signal processing unit 53 includes, for example, a fieldprogrammable gate array (FPGA) and generates a reference clock signal(for example, a clock of 27 MHz) indicating a reference of an operationof each component of the endoscope 2 and a synchronization signalindicating a start position of each frame and performs a predeterminedsignal process such as a noise eliminating process, a format convertingprocess, and a filter changing process on the digital image signal inputfrom the A/D converter 52 while supplying the signals to the timinggenerator 25.

Here, a detailed configuration of the image signal processing unit 53will be described. The image signal processing unit 53 includes at leasta vertical noise correcting unit 531, a format converter 532, a storageunit 533, a filter converter 534, an endoscope controller 535, and an IDinformation storing unit 536.

The vertical noise correcting unit 531 corrects a vertical noiseoccurring in the image signal input via the A/D converter 52.Specifically, the vertical noise correcting unit 531 includes acorrection data generating unit 531 a which calculates a statisticalvalue in each transfer line (each vertical transfer line to be describedlater) of the dummy signal output value included in a predeterminedrange and output from the dummy pixel 247 a plurality of times andgenerates correction data for correcting the image signal output fromthe unit pixel 230 based on the calculation result in each transfer lineand a correcting unit 531 b which corrects the image signal bysubtracting the correction data of the corresponding transfer line fromthe image signal output from the unit pixel 230 in each transfer linebased on the correction data of each transfer line generated by thecorrection data generating unit 531 a and outputs the corrected imagesignal to the format converter 532. Here, the statistical value is oneof an average value, a median value, and a mode in each transfer line ofthe dummy signal output value within a predetermined range (a normalvalue). The correction data generating unit 531 a may generatecorrection data for the dummy signal output value within thepredetermined range in each frame in which each of the plurality of unitpixels 230 generates the image signal.

The format converter 532 outputs the image signal output from the firstchip 21 by converting the image signal into a predetermined formatcorresponding to the processor 6 connected thereto. Specifically, theformat converter 532 performs a format converting process so that theformat of the image signal input from the vertical noise correcting unit531 after the correction of the vertical noise is converted into anarray of a Bayer image. More specifically, the format converter 532converts the format of the image signal into the image format of theBayer array by converting the arrangement so that a plurality of imagesignals read from the pixels corresponding to the R-filters and aplurality of image signals read from the pixels corresponding to theG_(r)-filters for the horizontal signal of one line of the even lines ofthe light receiving unit 23 read by the reading unit 24 are alternatelyarranged and by converting the arrangement so that a plurality of imagesignals read from the pixels corresponding to the B-filters and aplurality of image signals read from the pixels corresponding to theG_(b)-filters for the horizontal signal of one line of the odd lines ofthe light receiving unit 23 read by the reading unit 24 are alternatelyarranged. For example, the format converter 532 converts the format ofthe image signal into the format of the image of the Bayer array byarranging a plurality of image signals read from the pixelscorresponding to the R-filters in the odd vertical lines (2m+1, 2n) andarranging a plurality of image signals read from the pixelscorresponding to the G_(r)-filters in the even vertical lines (2m, 2n)for the horizontal signal of one line of the even lines of the lightreceiving unit 23 read by the reading unit 24 and arranging a pluralityof image signals read from the pixels corresponding to the G_(b)-filtersin the odd vertical lines (2m+1, 2n+1) and arranging a plurality ofimage signals read from the pixels corresponding to the B-filters in theeven vertical lines (2m, 2n+1) for the horizontal signal of one line ofthe odd lines of the light receiving unit 23 read by the reading unit24.

The storage unit 533 includes a first line memory 533 a which stores theimage signal of the R-filter of which the format is converted into thearray of the Bayer image by the format converter 532, a second linememory 533 b which stores the image signal of the G_(r)-filter, a thirdline memory 533 c which stores the image signal of the B-filter, and afourth line memory 533 d which stores the image signal of theG_(b)-filter.

The filter converter 534 converts the format of the filter of the imagesignal under the control of the endoscope controller 535. Specifically,the filter converter 534 converts the image signal of the Bayer filterinto an image signal of a complementary color filter under the controlof the endoscope controller 535.

The endoscope controller 535 controls elements constituting the imagesignal processing unit 53. The endoscope controller 535 acquires IDinformation of the processor 6 from an ID information storing unit 64 ofthe processor 6 and controls each element based on the acquiredinformation. The endoscope controller 535 serves as an acquisition unitaccording to the first embodiment. A method of acquiring informationnecessary to control each element is not limited to the method using theabove-mentioned ID information storing unit 64 and a voltage level of aconnector pin (not illustrated) or a combination thereof may be used asthe ID information.

The ID information storing unit 536 stores identification informationindicating the type of the endoscope 2, the type of the first chip 21(for example, the information of the color filter 26 or the shared pixelsystem), and the information of the format and the date of the imagesignal to be output.

The drive signal generator 57 generates the synchronization signalindicating the start position of each frame based on the reference clocksignal (for example, the clock signal of 27 MHz) supplied from theprocessor 6 and used as a reference of the operation of each of thecomponents of the endoscope 2 and outputs the synchronization signal tothe timing generator 25 of the imaging unit 20 via the transmissioncable 3 along with the reference clock signal. Here, the synchronizationsignal which is generated by the drive signal generator 57 includes ahorizontal synchronization signal and a vertical synchronization signal.

The processor 6 is a control device for performing overall control ofthe endoscope system 1. The processor 6 includes the power supply unit61, an image signal processing unit 62, a clock generator 63, and the IDinformation storing unit 64.

The power supply unit 61 generates a power supply voltage VDD andsupplies the generated power supply voltage VDD to the imaging unit 20via the connector 5 and the transmission cable 3 along with a groundGND.

The image signal processing unit 62 performs image processing such as asynchronizing process, a white balance (WB) adjusting process, a gainadjusting process, a gamma correcting process, a digital-to-analog (D/A)converting process, and a format converting process on the digital imagesignal subjected to the signal process in the image signal processingunit 53 so that the digital image signal is converted into the imagesignal and outputs the image signal to the display device 7.

The clock generator 63 outputs the reference clock signal to the drivesignal generator 57.

The ID information storing unit 64 stores identification informationindicating types of the processor 6, type information indicating typesof a color filter that is compatible with the image signal processingunit 62, format information that is compatible with the image signalprocessing unit 62, and ID information recording a model year.

The display device 7 displays an image captured by the imaging unit 20based on the image signal input from the image signal processing unit62. The display device 7 is configured by using a display panel such asa liquid crystal or an organic EL (Electro Luminescence).

Configuration of First Chip

Next, a detailed configuration of the above-mentioned first chip 21 willbe described. FIG. 4 is a circuit diagram illustrating a configurationof the first chip 21.

As illustrated in FIG. 4, the first chip 21 includes the timinggenerator 25, an output unit 31 (an amplifier), a vertical scanning unit241 (a row selecting circuit), a constant current source 242, a noiseeliminating unit 243 (a noise eliminating circuit), a column sourcefollower transistor 244, and a horizontal scanning unit 245.

The timing generator 25 generates various drive signals based on thereference clock signal and the synchronization signal and outputs thedrive signals to the vertical scanning unit 241 (the row selectingcircuit), the noise eliminating unit 243, and the horizontal scanningunit 245 of the reading unit 24 to be described later, respectively.

The vertical scanning unit 241 drives each of the unit pixels 230 of thelight receiving unit 23 using the constant current source 242 byapplying row selection pulses φT <M> and φR <M> to the selected rows <M>(M=0, 1, 2 . . . , m−1, m) of the light receiving unit 23 based on thedrive signals (φT and φR) input from the timing generator 25, the imagesignal and the pixel resetting noise signal are transferred to avertical transfer line 239 and are output to the noise eliminating unit243. In the first embodiment, the vertical scanning unit 241 serves as areading circuit and shares and reads the image signals from two unitpixels 230. In the first embodiment, the vertical transfer line 239serves as a transfer line.

The noise eliminating unit 243 eliminates the pixel resetting noisesignal and the output variation of each of the unit pixels 230 andoutputs an image signal which is photoelectrically converted in each ofthe unit pixels 230. The noise eliminating unit 243 will be described indetail later.

The horizontal scanning unit 245 applies a column selection signal φHCLK<N> to the selected column <N> (N=0, 1, 2 . . . , n−1, n) of the lightreceiving unit 23 based on the drive signal (φHCLK) supplied from thetiming generator 25 so that the image signal photoelectrically convertedin each of the unit pixels 230 is transferred and output to a horizontaltransfer line 258 (the second transfer line) via the noise eliminatingunit 243. In the first embodiment, the horizontal transfer line 258serves as a transfer part configured to transmit the image signal outputfrom each of the unit pixels 230.

The plurality of unit pixels 230 is arranged in a two-dimensional matrixform in the light receiving unit 23 of the first chip 21. Each of theunit pixels 230 includes a photoelectric conversion element 231 (aphotodiode), a photoelectric conversion element 232, a charge converter233, a transfer transistor 234 (a first transfer part), a transfertransistor 235, a charge converter resetting unit 236 (a transistor), apixel source follower transistor 237, a pixel output switch 238 (asignal output unit), and the dummy pixel 247 (the reference signalgenerating unit). In the specification, the transfer transistor fortransferring the signal charge from one or the plurality ofphotoelectric conversion elements and each of the photoelectricconversion elements to the charge converter 233 is referred to as a unitcell. That is, the unit cell includes one or the plurality ofphotoelectric conversion elements and a pair of transfer transistors andone unit cell is included in each of the unit pixels 230.

The photoelectric conversion element 231 and the photoelectricconversion element 232 photoelectrically convert incident light into asignal charge amount in response to the light amount and store thesignal charge amount. Cathodes of the photoelectric conversion element231 and the photoelectric conversion element 232 are respectivelyconnected to one ends of the transfer transistor 234 and the transfertransistor 235 and anodes thereof are connected to the ground GND. Thecharge converter 233 is configured as a floating diffusion capacitor(FD) and converts a charge stored in the photoelectric conversionelement 231 and the photoelectric conversion element 232 into a voltage.

The transfer transistor 234 and the transfer transistor 235 respectivelytransfer a charge from the photoelectric conversion element 231 and thephotoelectric conversion element 232 to the charge converter 233. Eachof the gates of the transfer transistor 234 and the transfer transistor235 is connected to signal lines to which the drive pulses (the rowselection pulses) φTa and φTb are supplied and the other ends thereofare connected to the charge converter 233. When the drive pulses φTa andφTb are supplied from the vertical scanning unit 241 via the signalline, the transfer transistor 234 and the transfer transistor 235 areturned on so that the signal charge is transferred from thephotoelectric conversion element 231 and the photoelectric conversionelement 232 to the charge converter 233.

The charge converter resetting unit 236 resets the charge converter 233to a predetermined potential. In the charge converter resetting unit236, one end is connected to the power supply voltage VDD, the other endis connected to the charge converter 233, and the gate is connected tothe signal line to which the drive pulse φR is supplied. When the drivepulse OR is supplied from the vertical scanning unit 241 via the signalline, the charge converter resetting unit 236 is turned on so that thesignal charge stored in the charge converter 233 is discharged and thecharge converter 233 is reset to a predetermined potential.

In the pixel source follower transistor 237, one end is connected to thepower supply voltage VDD, the other end is connected to one end of thepixel output switch 238, and the gate receives a signal (an image signalor a resetting signal) converted into a voltage by the charge converter233.

The pixel output switch 238 outputs the signal converted into a voltageby the charge converter 233 to the vertical transfer line 239. In thepixel output switch 238, the other end is connected to the verticaltransfer line 239 and the gate is connected to the signal line to whichthe drive pulse φX is supplied. When the drive pulse φX is supplied fromthe vertical scanning unit 241 to the gate of the pixel output switch238 via the signal line, the pixel output switch 238 is turned on sothat the image signal or the resetting signal is transferred to thevertical transfer line 239.

The dummy pixel 247 is provided in each transfer line of the unit pixel230. The dummy pixel 247 includes a pixel resetting unit 236 a and apixel source follower transistor 237 a. That is, in this configuration,the photoelectric conversion element 231 (the photodiode), the chargeconverter 233, and the transfer transistor 234 (the first transfer part)are omitted from the unit pixel 230.

The pixel resetting unit 236 a fixes the gate of the pixel sourcefollower transistor 237 a to a predetermined potential. In the pixelresetting unit 236 a, one end is connected to a power supply voltage VR,the other end is connected to the gate of the pixel source followertransistor 237 a, and the gate is connected to the signal line to whichthe drive signal φRdmy is supplied.

When the drive signal φRdmy is supplied from the timing generator 25 tothe gate of the pixel resetting unit 236 a via the signal line, thepixel resetting unit 236 a is turned on so that the gate of the pixelsource follower transistor 237 a is fixed to a predetermined potential(VRdmy).

In the pixel source follower transistor 237 a, one end is connected tothe power supply voltage VR supplied from a reference voltage generatingunit (not illustrated), the other end is connected to the verticaltransfer line 239, and the gate receives a predetermined potential(VRdmy). In the pixel source follower transistor 237 a with such aconfiguration, when a selection operation to be described later isperformed, the dummy signal (the column reference signal) correspondingto the predetermined potential VRdmy is transmitted to the verticaltransfer line 239 via the pixel source follower transistor 237 a.

Similarly to the normal unit pixel 230, in the first embodiment, if thedrive signal φRdmy is supplied to the gate of the pixel resetting unit236 a when the power supply voltage VR is at the level of the powersupply voltage VDD (for example, 3.3 V) and VRdmy (for example, 2 V) isinput, the pixel source follower transistor 237 a is turned on so thatthe dummy pixel 247 including the pixel resetting unit 236 a is selected(a selection operation). If the drive signal φRdmy is supplied to thegate of the pixel resetting unit 236 a when the power supply voltage VRis at the level of the non-selection voltage (for example, 1V) or VRdmy(for example, 1 V), the pixel source follower transistor 237 a is turnedoff so that the selection of the dummy pixel 247 including the pixelresetting unit 236 a is released (a non-selection operation).

In the constant current source 242, one end is connected to the verticaltransfer line 239, the other end is connected to the ground GND, and thegate receives a bias voltage Vbias1. The constant current source 242drives the unit pixel 230 by the constant current source 242 so that theoutput of the unit pixel 230 is read to the vertical transfer line 239.The signal read to the vertical transfer line 239 is input to the noiseeliminating unit 243.

The noise eliminating unit 243 includes a transfer capacitor 252 (ACcoupling capacitor) and a clamp switch 253 (a transistor).

In the transfer capacitor 252, one end is connected to the verticaltransfer line 239 and the other end is connected to the column sourcefollower transistor 244.

One end of the clamp switch 253 is connected to the signal line to whicha clamp voltage Vclp is supplied from the reference voltage generatingunit (not illustrated). In the clamp switch 253, the other end isconnected between the transfer capacitor 252 and the column sourcefollower transistor 244 and the gate receives a drive signal φVCL fromthe timing generator 25. The image signal which is input to the noiseeliminating unit 243 is an optical noise signal including a noisecomponent.

When the drive signal φVCL is input from the timing generator 25 to thegate of the clamp switch 253, the clamp switch 253 is turned on, so thatthe transfer capacitor 252 is reset by the clamp voltage Vclp suppliedfrom the reference voltage generating unit (not illustrated). The imagesignal of which the noise is eliminated by the noise eliminating unit243 is input to the gate of the column source follower transistor 244.

Since the noise eliminating unit 243 with such a configuration does notneed the sampling capacitor, the capacitance of the transfer capacitor(AC coupling capacitor) 252 may be a capacitance which is enough for theinput capacitance of the column source follower transistor 244. Thenoise eliminating unit 243 can decrease an occupied area in the firstchip 21 by the absence of the sampling capacitor.

In the column source follower transistor 244, one end is connected tothe power supply voltage VDD, the other end is connected to one end of acolumn selection switch 254 (a second transfer part), and the gatereceives the image signal from which noise is eliminated by the noiseeliminating unit 243.

In the column selection switch 254, one end is connected to the otherend of the column source follower transistor 244, the other end isconnected to the horizontal transfer line 258 (the second transferline), and the gate is connected to the signal line to which the drivesignal φHCLK <M> is supplied from the horizontal scanning unit 245. Whenthe drive signal φHCLK <M> is supplied from the horizontal scanning unit245 to the gate of the column selection switch 254 of the column <M>,the column selection switch 254 is turned on so that the signal of thevertical transfer line 239 of the column <M> (the image signal fromwhich noise is eliminated by the noise eliminating unit 243) istransferred to the horizontal transfer line 258.

In a horizontal reset transistor 256, one end is connected to the groundGND, the other end is connected to the horizontal transfer line 258, andthe gate receives a drive signal φHCLR from the timing generator 25.When the drive signal φHCLR is input from the timing generator 25 to thegate of the horizontal reset transistor 256, the horizontal resettransistor 256 is turned on so that the horizontal transfer line 258 isreset.

In a constant current source 257, one end is connected to the horizontaltransfer line 258, the other end is connected to the ground GND, and abias voltage Vbias2 is applied to the gate. The constant current source257 reads the image signal from the vertical transfer line 239 to thehorizontal transfer line 258. The image signal or the dummy signal whichis read to the horizontal transfer line 258 is input to the output unit31.

The output unit 31 amplifies the image signal and the dummy signal (thereference signal which is used as a reference when the transfer line iscorrected) from which noise is eliminated if necessary and outputs theamplified signal (Vout).

Format Converting Process

Next, a format converting process which is performed by the formatconverter 532 will be described. FIG. 5 is a schematic diagramillustrating an outline of the format converting process which isperformed on the even lines of the light receiving unit 23 by the formatconverter 532. FIG. 6 is a schematic diagram illustrating an outline ofthe format converting process which is performed on the odd lines of thelight receiving unit 23 by the format converter 532. In (a) of FIG. 5and (a) of FIG. 6, the exemplary image signal input after the correctionof the vertical noise by the vertical noise correcting unit 531 isshown. In (b) of FIG. 5 and (b) of FIG. 6, the exemplary image signalafter the conversion of the format by the format converter 532 is shown.In FIG. 5, the unit pixel 230 is formed such that the R-filter isdisposed on the photoelectric conversion element 231 and theG_(r)-filter is disposed on the photoelectric conversion element 232. InFIG. 6, the unit pixel 230 is formed such that the G_(b)-filter isdisposed on the photoelectric conversion element 231 and the B-filter isdisposed on the photoelectric conversion element 232. In FIGS. 5 and 6,“n” indicates an integer.

First, a format converting process which is performed on the even linesof the light receiving unit 23 by the format converter 532 will bedescribed. As illustrated in FIG. 5, the format converter 532 performs aformat converting process in which the image signal input from thevertical noise correcting unit 531 after the correction of the verticalnoise is converted into the array of the Bayer image. Specifically, theformat converter 532 stores the image signals of all R-filters of thehorizontal signal of one line of the even line (2n) of the lightreceiving unit 23 (the image sensor) in the first line memory 533 a byarranging the image signals in the odd lines (2m+1, 2n) of the oddvertical lines and stores the image signals of all G_(r)-filters in thesecond line memory 533 b by arranging the image signals in the evenlines (2m, 2n) of the vertical lines. More specifically, as illustratedin (b) of FIG. 5, the format converter 532 converts the image signalsinto the Bayer image array so that the image signals (R₁ to R_(n)) ofthe R-filters and the image signals (G_(r1) to G_(rn)) of theG_(r)-filters of the image signals input after the correction of thevertical noise using the vertical noise correcting unit 531 in thehorizontal signal of one line of the even lines (2n) of the lightreceiving unit 23 (the image sensor) are alternately arranged(R₁G_(r1)R₂G_(r2) . . . R_(n)G_(rn)) Subsequently, the format converter532 stores the image signal converted into the Bayer array in the firstline memory 533 a and the second line memory 533 b, respectively.

Next, a format converting process which is performed on the odd lines ofthe light receiving unit 23 by the format converter 532 will bedescribed. As illustrated in FIG. 6, the format converter 532 stores theimages signals of all B-filters of the horizontal signal of one line ofthe odd lines (2n+1) of the light receiving unit 23 (the image sensor)in the third line memory 533 c by arranging the image signals in the oddlines (2m+1, 2n+1) of the vertical lines and stores the image signals ofall G_(b)-filters in the fourth line memory 533 d by arranging the imagesignals in the even lines (2m, 2n+1) of the vertical lines. Morespecifically, as illustrated in (b) of FIG. 6, the format converter 532converts the image signals into the Bayer image array so that the imagesignals (B₁ to B_(n)) of the B-filters and the image signals (G_(b1) toG_(bn)) of the G_(r)-filters of the image signals input after thecorrection of the vertical noise using the vertical noise correctingunit 531 in the horizontal signal of one line of the odd lines (2n+1) ofthe light receiving unit 23 (the image sensor) are alternately arranged(G_(b1)B₁G_(b2)B₂ . . . G_(bn)B_(n)). Subsequently, the format converter532 stores the image signal converted into the Bayer array in the thirdline memory 533 c and the fourth line memory 533 d, respectively.

In this way, the format converter 532 stores the image signals of allR-filters of the horizontal signals of one line of the even lines (2n)of the image signals input after the correction of the vertical noiseusing the vertical noise correcting unit 531 in the first line memory533 a by arranging the image signals in the odd lines (2m+1, 2n) of thevertical lines and stores the image signals of all G_(r)-filters in thesecond line memory 533 b by arranging the image signals in the evenlines (2m, 2n) of the vertical lines. At the same time, the formatconverter 532 stores the image signals of all B-filters of thehorizontal signal of one line in the odd lines (2n+1) of the lightreceiving unit 23 (the image sensor) in the third line memory 533 c byarranging the image signals in the odd lines (2m+1, 2n+1) of thevertical lines and stores the image signals of all G_(b)-filters in thefourth line memory 533 d by arranging the image signals in the evenlines (2m, 2n+1) of the vertical lines. Accordingly, the image signal ofthe first chip 21 read by the pixel sharing method can be converted intothe Bayer format. As a result, since the image signal processing unit 62corresponding to the pixel sharing method does not need to be providedin the processor 6, high user-friendliness and excellent versatility areobtained.

Converting Method of Filter Converter

Next, a converting method of the filter converter 534 will be described.The filter converter 534 acquires the image signal of the Bayer arrayfrom each of the first line memory 533 a, the second line memory 533 b,the third line memory 533 c, and the fourth line memory 533 d under thecontrol of the endoscope controller 535, and converts the acquired imagesignal of the Bayer array into a color filter that is compatible withthe processor 6. Specifically, the endoscope controller 535 causes thefilter converter 534 to perform conversion into a filter that iscompatible with the processor 6 based on types of the color filtercompatible with the image signal processing unit 62 included in the IDinformation acquired from the ID information storing unit 64 of theprocessor 6. More specifically, as illustrated in FIG. 7, if the imagesignal processing unit 62 of the processor 6 is compatible with thecomplementary color filter, the filter converter 534 converts the imagesignal of the Bayer filter into the image signal of the complementarycolor filter and outputs the image signal to the image signal processingunit 62.

For example, the filter converter 534 generates the image signals of thecomplementary color of cyan (hereinafter, a “Cy-filter”) and green(hereinafter, a “G-filter”) in the odd lines forming the image and theimage signals of the complementary color of yellow (hereinafter, a“Y-filter”) and magenta (hereinafter, a “Mg-filter”) in the even linesbased on the image signal of the Bayer array acquired from each of thefirst line memory 533 a, the second line memory 533 b, the third linememory 533 c, and the fourth line memory 533 d.

Specifically, as illustrated in FIG. 7, the filter converter 534converts the image signal of the Bayer filter T1 into the image signalof the complementary color filter T2 by calculating the image signal ofthe Cy-filter and the image signal of the G-filter of the complementarycolor filter using the image signal (the blue component) of the B-filterstored in the third line memory 533 c and the image signal (the secondgreen component) of the G_(b)-filter stored in the fourth line memory533 d. More specifically, the filter converter 534 calculates the imagesignal of the Cy-filter of the complementary color filter by adding theimage signal of the B-filter stored in the third line memory 533 c andthe image signal of the G_(b)-filter stored in the fourth line memory533 d and calculates the image signal of the G-filter of thecomplementary color filter T2 by using the image signal of theG_(b)-filter stored in the fourth line memory 533 d.

The filter converter 534 converts the image signal of the Bayer filterT1 into the image signal of the complementary color filter T2 bycalculating the image signal (the magenta component) of the Mg-filterand the image signal (the yellow component) of the Y-filter of thecomplementary color filter using the image signal (the red component) ofthe R-filter stored in the first line memory 533 a, the image signal(the first green component) of the G_(r)-filter stored in the secondline memory 533 b, and the image signal (the blue component) of theB-filter stored in the third line memory 533 c.

Specifically, the filter converter 534 calculates the image signal ofthe Y-filter of the complementary color filter by adding the imagesignal of the R-filter stored in the first line memory 533 a and theimage signal of the G_(r)-filter stored in the second line memory 533 band calculates the image signal of the Mg-filter of the complementarycolor filter T2 by adding the image signal of the R-filter stored in thefirst line memory 533 a, the image signal of the G_(r)-filter stored inthe second line memory 533 b, and the image signal of the B-filterstored in the third line memory 533 c.

In this way, the filter converter 534 acquires the image signal of theBayer array from each of the first line memory 533 a, the second linememory 533 b, the third line memory 533 c, and the fourth line memory533 d under the control of the endoscope controller 535 and converts theacquired image signal of the Bayer array into the image signal of thecolor filter corresponding to the processor 6. When the image signalprocessing unit 62 of the processor 6 can correspond to the image signalof the Bayer filter, the filter converter 534 outputs the image signalto the processor 6 without converting the filter and converting theimage signals of the color components of the first line memory 533 a tothe fourth line memory 533 d. As a result, since the image signalprocessing unit 62 corresponding to the filter of the Bayer array maynot be provided in the processor 6, high user-friendliness and excellentversatility are obtained.

According to the first embodiment, the format converter 532 stores theimage signals of all R-filters of the horizontal signal of one line ofthe even lines (2n) of the image signals input after the correction ofthe vertical noise using the vertical noise correcting unit 531 in thefirst line memory 533 a by arranging the image signals in the odd lines(2m+1, 2n) of the vertical lines and stores the image signals of allG_(r)-filters in the second line memory 533 b by arranging the imagesignals in the even lines (2m, 2n) of the vertical lines. At the sametime, the format converter 532 stores the image signals of all B-filtersof the horizontal signal of one line of the odd lines (2n+1) in thethird line memory 533 c by arranging the image signals in the odd lines(2m+1, 2n+1) of the vertical lines and stores the image signals of allG_(b)-filters in the fourth line memory 533 d by arranging the imagesignals in the even lines (2m, 2n+1) of the vertical lines. Accordingly,the image signal read by the pixel sharing method can be converted intothe Bayer format. As a result, since the image signal processing unit 62corresponding to the pixel sharing method may not be provided in theprocessor 6, high user-friendliness and excellent versatility areobtained.

Further, according to the first embodiment, the filter converter 534acquires the image signal of the Bayer array from each of the first linememory 533 a, the second line memory 533 b, the third line memory 533 c,and the fourth line memory 533 d under the control of the endoscopecontroller 535 and converts the acquired image signal of the Bayer arrayinto the filter corresponding to the processor 6. As a result, since theimage signal of the Bayer filter is converted into the image signal ofthe complementary color filter even when the processor 6 can correspondto the image signal of the complementary color filter, highuser-friendliness and excellent versatility are obtained.

Further, according to the first embodiment, since the format converter532 converts the format of the image signal input from the verticalnoise correcting unit 531 after the correction of the vertical noise, ahigh-quality image can be obtained.

Second Embodiment

Next, a second embodiment of the present invention will be described. Inthe above-described first embodiment, the endoscope 2 changes thecontent of the output image signal in response to the type of theprocessor 6, but in the second embodiment, the processor changes thecontent of the image process in response to the endoscope. The samereference numerals will be used to designate the same elements as thoseof the endoscope system 1 according to the first embodiment and theexplanation thereof will be omitted.

Configuration of Endoscope System

FIGS. 8A and 8B are block diagrams illustrating a function of a mainpart of an endoscope system according to the second embodiment of thepresent invention. As illustrated in FIGS. 8A and 8B, an endoscopesystem 1 a includes an endoscope 2 a, a processor 6 a, and the displaydevice 7.

Configuration of Endoscope

First, a configuration of the endoscope 2 a will be described. Theendoscope 2 a includes a color filter 26 a and a connector 5 a insteadof the color filter 26 of the first chip 21 and the connector 5 of theendoscope 2 according to the above-described first embodiment. The colorfilter 26 a is configured as a complementary color filter (CyGYMg) (forexample, the complementary color filter T2 of FIG. 7).

The connector 5 a includes the AFE unit 51, the A/D converter 52, animage signal processing unit 53 a, the ID information storing unit 536,and the drive signal generator 57.

The image signal processing unit 53 a includes, for example, an FPGA,generates a reference clock signal (for example, a clock of 27 MHz)indicating a reference of an operation of each component of theendoscope 2 a and a synchronization signal indicating a start positionof each frame, and performs a predetermined signal process such as anoise eliminating process on the digital image signal input from the A/Dconverter 52 while supplying the signals to the timing generator 25.

Configuration of Processor

Next, a configuration of the processor 6 a will be described. Theprocessor 6 a includes the power supply unit 61, a first image signalprocessing unit 62 a, a second image signal processing unit 62 b, theclock generator 63, an ID information acquiring unit 65, a switchingunit 66, and an image processing controller 67.

The first image signal processing unit 62 a performs image processingsuch as a synchronizing process, a white balance (WB) adjusting process,a gain adjusting process, a gamma correcting process, adigital-to-analog (D/A) converting process, and a format convertingprocess on the digital image signal (the image signal of thecomplementary color filter) subjected to the signal process in the imagesignal processing unit 53 a and input via the switching unit 66 so thatthe digital image signal is converted into the image signal and outputsthe image signal to the display device 7.

The second image signal processing unit 62 b performs image processingsuch as a format converting process, a filter converting process, asynchronizing process, a white balance (WB) adjusting process, a gainadjusting process, a gamma correcting process, and a digital-to-analog(D/A) converting process on the digital image signal (the image signalof the Bayer filter) subjected to the signal process in the image signalprocessing unit 53 a and input via the switching unit 66 so that thedigital image signal is converted into the image signal and outputs theimage signal to the display device 7. The second image signal processingunit 62 b includes at least the vertical noise correcting unit 531, theformat converter 532, the storage unit 533, and the filter converter 534according to the above-described first embodiment.

The ID information acquiring unit 65 acquires the ID information of theendoscope 2 a from the ID information storing unit 536 of the endoscope2 a connected to the processor 6 a and outputs the acquired IDinformation to the image processing controller 67.

Under the control of the image processing controller 67, the switchingunit 66 switches an output destination of the image signal input fromthe endoscope 2 a in response to the type of the endoscope 2 a connectedto the processor 6 a.

The image processing controller 67 includes a CPU or the like andperforms overall control of the operation of each component of theprocessor 6 a. The image processing controller 67 controls the switchingunit 66 based on the ID information input from the ID informationacquiring unit 65 to switch an output destination of the image signalinput from the endoscope 2 a. Specifically, the image processingcontroller 67 switches the switching unit 66 so that the image signalinput from the endoscope 2 a is input to the first image signalprocessing unit 62 a when the filter information of the endoscope 2 aincluded in the ID information input from the ID information storingunit 536 is the complementary color filter and switches the switchingunit 66 so that the image signal input from the endoscope 2 a is inputto the second image signal processing unit 62 b when the filterinformation of the endoscope 2 a included in the ID information inputfrom the ID information acquiring unit 65 is the Bayer filter.

According to the second embodiment, the processor 6 a includes twofilters, that is, the first image signal processing unit 62 a and thesecond image signal processing unit 62 b respectively corresponding tothe Bayer filter and the complementary color filter and the imageprocessing controller 67 switches the output destination to which theimage signal is output by the switching unit 66 to the first imagesignal processing unit 62 a or the second image signal processing unit62 b based on the ID information of the endoscope 2 a input from the IDinformation acquiring unit 65. Accordingly, since the image signalsubjected to an image process corresponding to the endoscope 2 aconnected to the processor 6 a can be output to the display device 7even when different types of endoscopes 2 a are connected to theprocessor 6 a, versatility can be improved.

Other Embodiments

In the first and second embodiments, the image signal processing unit isprovided in the connector, but may be provided in, for example, theoperating unit of the endoscope.

According to some embodiments, it is possible to provide an endoscopewhich has high user-friendliness and excellent versatility.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An endoscope comprising: an image sensorincluding: a plurality of pixels arranged two-dimensionally, theplurality of pixels being configured to receive external light togenerate a plurality of image signals in accordance with a lightreceiving amount; and a plurality of reading circuits sharingpredetermined number of pixels with one another and configured to readthe plurality of image signals to transfer lines; a format converterconfigured to convert the plurality of image signals output from theimage sensor into a predetermined format corresponding to a processingdevice for performing image processing on the plurality of imagesignals; and a connector including the format converter and configuredto be connected to the processing device, wherein the image sensorincludes a color filter of a Bayer array in which a red filter forpassing a red component and a first green filter for passing a greencomponent are alternately arranged in even lines of horizontal lines ofthe plurality of pixels, and a second green filter for passing a greencomponent and a blue filter for passing a blue component are alternatelyarranged in odd lines of the horizontal lines of the plurality ofpixels, wherein the plurality of reading circuits is configured to: readfirst image signals of the plurality of image signals from pixelscorresponding to the red filter and read second image signals of theplurality of image signals from pixels corresponding to the first greenfilter in the even lines of the horizontal lines of the image sensor;and read third image signals of the plurality of image signals frompixels corresponding to the second green filter and read fourth imagesignals of the plurality of image signals from pixels corresponding tothe blue filter in the odd lines of the horizontal lines of the imagesensor, and wherein the format converter is configured to convert theplurality of image signals into an image format for the Bayer array byconverting an arrangement in the color filter such that the first imagesignals and the second image signals are alternately arranged in theeven lines of the image sensor read by the plurality of readingcircuits, and the third image signals and the fourth image signals arealternately arranged in the odd lines of the image sensor read by theplurality of reading circuits.
 2. The endoscope according to claim 1,wherein the image sensor includes a plurality of dummy pixels providedfor each of the transfer lines in an arrangement of the plurality ofpixels, the plurality of dummy pixels being configured to generate andoutput dummy signals to be used for correcting the plurality of imagesignals, wherein the endoscope further comprises: a correction datagenerating unit configured to calculate, for each of the transfer lines,a statistical value of output values of the dummy signals output aplurality of times from the plurality of dummy pixels, and generate, foreach of the transfer lines, correction data for correcting the pluralityof image signals based on the statistical value; and a correcting unitconfigured to correct the plurality of image signals based on thecorrection data generated by the correction data generating unit, andwherein the format converter is configured to convert the plurality ofimage signals corrected by the correcting unit into the predeterminedformat.
 3. The endoscope according to claim 1, further comprising: anacquisition unit configured to acquire, from the processing deviceconnected to the endoscope, identification information including typeinformation indicating types of a color filter that is compatible withthe processing device; and a filter converter configured to convert theplurality of image signals converted by the format converter into imagesignals of the color filter that is compatible with the processingdevice, based on the identification information acquired by theacquisition unit.